An interesting group of animals which may be divided into four sections:

• snakes
• tortoises and turtles
• crocodiles

With the exception of the crocodiles, these groups are represented by species recorded at the garden.

Snakes

Snakes are not seen as often as may be expected as many are nocturnal and others avoid areas where there are lots of people. Snakes do not possess external ears or eardrums and "hear" by feeling vibration through their bodies. They are also not able to blink as they have no moveable eyelids, only a transparent covering which is shed when the snake moults. It is thought that snakes and lizards are probably descended from a common lizard-like ancestor and although they are related there are fundamental differences between them, which is not necessarily the possession of legs as one would think! Pythons have external remnants of hindlegs and there are specialised burrowing skinks which have no external signs of limbs at all.

Snakes have adapted to life in a wide range of habitats from the dry, hot desert regions to the sea. They perform an important ecological function as they are predators and also provide a service to man in helping to keep rodent numbers down to a level where they are not destructive.

Checklist of snakes

Lizards

Lizards are perhaps the most familiar reptiles to most people. Like snakes they have adapted to many different environments and range in size from the tiny dwarf geckoes to the Nile water monitor which may reach 2m in length. Most possess an ingenious method of escaping potential predators which leaves the confused hunter clutching a useless, twitching tail-tip while the lizard dashes into a safe crevice. When the predator grabs at the fleeting lizard, it is often only the tail which is caught. The tail parts company with the rest of the body relatively easily which helps minimise damage to the lizard. In most cases, the lost tail can be regenerated. Male rock agamas in their brilliant breeding colours are often visible on the rocks from the Black Eagle view point near the top of the waterfall. The water monitor or leguan may occasionally be seen slipping into the water at the dam or along the river where they hunt crabs, frogs, young birds, eggs and fish. The juveniles can be recognised by their beautiful yellow and black coloration.

An unusual lizard which lives in amongst the leaves of trees and shrubs is the chameleon. Its unique appearance has dual qualities of stealth and camouflage. Perhaps the most famous of its features is the ability to change colour to suit the background. The chameleon moves invisibly through the shrubbery with a hesitant motion emulating the stirring of leaves by a breeze. This both protects it from potential predators and allows it to sneak up on its own prey undetected. This consists mainly of insects, particularly beetles and grasshoppers in the case of our common flap-necked chameleon. Their strange protruding eyes can swivel independently of each other allowing scanning for prey and predators simultaneously. Once an insect is spotted, the chameleon shoots out its tongue and captures it. This happens at lightning speed and one can imagine that the insect is taken by surprise. The tongue is unique, it "telescopes" in the mouth of the chameleon when not required. (The same mechanism as a fireman's ladder or adjustable tripod legs.) The tongue can extend to a distance greater than the chameleon's body length to capture prey! The tail is prehensile and curls around twigs providing support. The feet have toes which are joined together in two groups on each foot, forming a "clamp" which can grasp at moving leaves and twigs. These fascinating animals are rarely sighted in the Garden.

Tortoises and Terrapins

There are two species of tortoise which occur in the Garden naturally; the mountain leopard tortoise (Geochelone pardalis) and the hinged tortoise (Kinixys belliana).

The mountain leopard tortoise is the largest of the Southern African tortoises and may exceed 70cm in length. These larger specimens are at least 30 years old, possibly more. A young tortoise grows very quickly at first to gain the sort of size where it less vulnerable to predators. Subsequent growth is much slower. Sexual maturity is reached at about 15 years. Newly hatched tortoises have to dig their way out of their underground nests, often waiting until the rains have begun for the earth to be soft enough. The coloration and markings vary with age, but are predominately a yellowish background with irregular dark blotches.

The hinged tortoise is of a smaller size, up to 20 cm. As its name suggests it may be recognised by a joint across the shell in the hind quarter. This hinge allows enough movement for the tortoise to close the gap between the shell and base plate thereby protecting the hind section of the tortoise. These tortoises eat various plants, fruit, mushrooms and some invertebrates such as the giant land snail and the pill millipede. They may also eat carrion and like other tortoise species they will gnaw on bones to obtain calcium for the growth of their shells.

The Cape or marsh terrapin (Pelomedusa subrufa) can often be seen from the birdhide, basking on the islands in the Sasol Dam. It is omnivorous and will feed on water-plants, frogs, fish and carrion. It has also been known to lie in wait for birds coming to the water's edge to drink and bathe.

Checklist of tortoises and terrapins

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